



5; 



15. 



<5 

 55J 



Vertical and honznntal disuihulion ol celK 



69 61 57 



10 telK/m 



5 10 15 



Fig. 4. Distribution ofbacterial population in the Chukchi Sea, summer 1 ? 



l,108x lO'cells/ml and 23. 14and24.94mgC/m\ respectively. 

 Minimum numbers and their biomass occurred at Station 57. 

 where values averaged 446 x 10' cells/ml and 10.49 mg C/m\ 



In the central basin, highest bacterial activity compared 

 with the other study sites. Maximum dark CO, assimilation by 

 bacteria occurred at Station 64, where the rates equaled that of 

 eutrophic waters. Minimum values occurred at Station 74. 

 Vertically, numbers and biomass of bacterioplankton peaked 

 between 0.5 and 25 m thick relative to values in the microlayer 

 and near-bottom waters. 



In conclusion, microbiological studies were made for the 

 first time in the Chukchi Sea. Water masses of the Chukchi Sea 

 showed a high level of microbiocenoses growth comparable to 

 mesotrophic waters. Additionally , bacterial numbers, biomass, 

 and activity in the waters of the Chukchi Sea exceeded those 

 found in the Bering Sea. 



4.1.2 Thymidine Incorporation, Frequency of 

 Dividing Cells, and Growth Rates of 

 Bacterioplankton 



ROGER B. HANSON and CHARLES Y. ROBERTSON 



Skidaway Institute of Oceanography. Savannah. Georgia. USA 



Introduction 



The Third Joint US-USSR Bering & Chukchi Seas 

 Expedition offered a comparative regional and depth analysis 

 of bacterioplankton in the ice-free Chirikov basin and the south 

 Bering Sea during late July and early August 1 988. This study 

 focused primarily on the Chirikov basin, the region between 

 the St. Lawrence Island and the Bering Strait. Two deep-water 

 stations in the south Bering Sea ecosystem were also examined. 



The principal objectives were to characterize the spatial 

 distribution and potential growth rate of bacterioplankton, to 

 estimate bacterioplankton productivity, and to assess their 

 importance relative to primary production in the western and 

 eastern Chirikov basin. The results from this study provided 

 some essential, first time estimates of bacterioplankton 

 production, growth rate, and biomass in the shallow ecosystem 

 of the northern Bering Sea and in deep waters of the south 

 Bering Sea. 



60 



